Raven released both Jedi Knight 2 Jedi Outcast and Jedi Knight 3 Jedi Academy sources under the GLP licence after Lucas Arts got shut down by Disney.
Jedi Academy sources -> http://sourceforge.net/projects/jediacademy/
Jedi Outcast sources -> http://sourceforge.net/projects/jedioutcast/
And there is already a project to upgrade the sources (mainly via backporting ioQuake3 they said) in GitHub called OpenJK
Link -> https://github.com/Razish/OpenJK